Fully Integrated Motion Controllers Power Mobile, Social Robots

When most people think of robots, movie-made science fiction stars come to mind -- C3PO and R2D2 from the Star Wars franchise, B9 from Lost in Space, or even the phrase “GORT! Klaatu barada nikto!” spoken by Patricia Neal’s character to the flexible metal, 8-ft-tall, laser-beam-shooting robot in The Day the Earth Stood Still. For those in manufacturing or engineering, minds turn to the latest generation of industrial robots -- multi-axis, jointed robotic arms that can weld, pick-and-place, package, and press faster than any human possibly could.

Industrial robots have become staples in medical, packaging, and automotive industries because of their numerous benefits, including increased efficiency, higher throughput, and lack of repetitive motion fatigue. Inside the robots, advancements in motion control have allowed these machines to perform complex tasks with a precision impossible for human operators.

KUKA industrial robots hard at work.

Though most industrial robots can move in a multi-axis fashion, their largest limitation is their fixed position on the factory (or laboratory) floor. While they have the advantage of main AC power drops for a nearly limitless power source, it’s also a leash binding them to a small work area.

Enter the field of mobile robotics -- capable of movement in (almost) any environment. Recently, mobile robots have gained popularity in distribution centers and factory floors, with companies like Amazon stealing headlines in 2012 by acquiring Kiva Systems (a mobile robotics company).

While advanced controllers have exponentially increased the number and kind of tasks industrial robots can accomplish, mobile robotics brings a new set of challenges to motion control that favors the compact, increasingly integrated motion control systems.

“As soon as (robots) go mobile, everything changes -- the way you chose drives, power supplies, motors and controllers, everything. The efficiencies change because mobile robots are typically low voltage DC systems,” said Hack Summer, application technology manager of Moog Animatics. He went on to say:

When specifying motion control systems for mobile robotics, it first comes down to power. Mobile robots don’t have the luxury of 480V three-phase AC mains coming in, and that’s where fully integrated motion is ideal. Most standard servos run off of 120V AC or 240V AC that rectify over to 160V DC or 300V DC, respectively, but you can’t typically get 160V DC batteries. If you want it to be mobile, you need a motion control system that will run off of 48V or less.

The compact SmartMotor was designed to operate at or below 48V DC while providing torque ranges comparable to larger, higher-voltage AC-powered servo systems. This kind of motion control system is ideal for battery-operated equipment such as mobile robots. Given the low voltage and high efficiency of the SmartMotor servo and drive stages, we’ve reduced weight, size, and power requirements. This equates to longer run time on the batteries and overall system performance gains.

Have robot, will travel
Mobile robots with advanced motion control systems aren’t just for the flat production floor. Their environments can include travel through water and by air, where mobile robotics migrates toward autonomy, such as with Adept’s Lynx AIV (autonomous indoor vehicle).

According to Summer:

Mobile robotics leans heavily on integrated motion because of the ‘mobile controller’ issue. These robots can’t be wheeling huge control cabinets behind them stacked with drives and controllers for each motor inside the robot, so the controller has to be advanced enough to deal with all of the robot tasks at hand while still being compact.

By using integrated controls, each axis of motion may sustain control of its local function. For example, an autonomous mobile robot with a hinged arm may need to hold the ‘wrist’ level to the ground. The integrated control of the wrist axis can use the phase adjust mode in the SmartMotor to keep the wrist level no matter what the arm does. For each additional axis another dedicated motion controller has been added to the system, bringing more control and processing power up to the system-level.

The use of remotely controlled mobile robots to offer a therapeutic experience to autistic children is wonderful idea. Further research in this area and more sophisticated AI routines could give rise to even better treatment programs for such children.

I agree, Greg - a good reminder of how power requirements often drive design strategies. It will be very interesting to watch the progress of mobile robots and the types of capabilities that will be integrated into their design as the constraints of current technology are pushed further and further out.

I think this is a wonderful application – Doornik's statement makes perfect sense to me: "In the robot's presence, a magical change occurs where intellect, physical appearance, abilities, or handicaps suddenly become unimportant. Such a therapeutic experience is made possible by the non-human attributes of the robot. His interlocutors are never placed in a situation where the children feel obliged to 'compare' themselves to the robot or be concerned with how the robot may perceive them."

We use our horses in therapeutic horse ministry for the very same reasons – with often miraculous results. I applaud any type of technology that can work to enhance the lives of these children!

There have been a few applications with a fairly standard robot on a platform able to move along a single linear axis of any length. That was for a robot that could follow the production line. Sort of a compromise between fixed and totally free. Power was from a hanging cable, 3-phase & about 8 amps. Way cheaper and simpler than a battery supply, and it was simple to program as one more axis. "Free range" robots are a whole different story, with a totally different set of applications. So the other important thing is that "free" robots probably would need to be made for those different applications, since the standard six-axis robot is simply not suitable for a large portion of what the fixed anchor robots would be doing.

Good point about how going mobile changes the design strategies for drives, power supplies, motors, etc. due to the use of low voltage DC components. This should produce advances in these areas as more low power mobile robots are designed.

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